This die cut roll comprises a combination of a die cutter formed by providing projecting pressure cutting blades, which are formed in accordance with the shape of a sheet type product to be cut, on a surface of a rotary driving roll, and an anvil roll. A sheet type work to be cut is made to run between the two rolls, and the die cutter is rotated in an anvil roll-pressing manner so as to cut the sheet type work to a predetermined shape with the projecting pressure cutting blades.
Many attempts have heretofore been made to improve the cutting quality of the cutting blades and prolong the lifetime thereof. For example, Japanese Patent Registration No. 2593570 discloses that the relation between the hardness of pressing ends of cutting blades and that of a surface of an anvil roll has influence upon the lifetime of the cutting blades, and that, when a hardness difference therebetween is set to more than 0.1, the lifetime of the cutting blades increases more than ten times. Japanese Patent Laid-Open No. 227798/1995 discloses the selection of specific materials for creating a proper hardness difference.
Japanese Patent Laid-Open No. 71999/1996 discloses the prolonging of the lifetime of cutting blades with respect to the shape thereof, i.e., it discloses the possibility of increasing the lifetime of cutting blades by setting the cutting blade width of an axial portion thereof smaller than that of a circumferential portion thereof. Japanese Patent Laid-Open No. 72000/1996 discloses crowned die cutters provided in both a die cut roll of a two-shaft driving system in which an anvil roll is driven by two synchronously rotated shafts, and a die cut roll of a single-shaft driving system in which a die cutter alone is driven with an anvil roll driven thereby.
Japanese Patent Laid-Open No. 267299/1997 discloses the techniques for improving the cutting quality of cutting blades without spoiling the strength thereof, by setting the angles .alpha., .beta. (apex angle becomes .alpha.+.beta.) of two inclined surfaces of each edge of the cutting blades with respect to a radius vector to .alpha..noteq..beta., 0.ltoreq..alpha..ltoreq.60.degree., 25.ltoreq..beta..ltoreq.80.degree. and 5.ltoreq..beta.-.alpha..ltoreq.80.degree..
The mode of abrasion of a die cut roll is complicated, and various things cause imperfect cutting of a work, chipping of projecting pressure cutting blades, early deterioration of the cutting performance of edges of the projecting pressure cutting blades and a decrease in the lifetime thereof to occur. Moreover, die cut rolls of different driving systems have greatly different modes of abrasion of a die cutter and an anvil roll, i.e., in a certain driving system, non-uniform abrasion of the rolls occurs, or a decrease occurs in the lifetime of the edge of the cutting blades ascribed to the chipping thereof. When the projecting pressure cutting blades on the surface of the die cutter are formed discontinuously in the rotational direction thereof, an extreme repeated stress is exerted on the pressure cutting blades, and a rate of abrasion thereof increases, so that the imperfect cutting of a work and the chipping of the pressure cutting blades occur. Even when the projecting pressure cutting blades are provided over the entire circumferentially continuous portion of the die cutter with the axial cutting length thereof decreasing due to the shape of the same, the concentration of stress on the blades causes an increase in the rate of abrasion thereof and the chipping thereof.